Maneuvering predictions for fast monohulls in early design stage

The present paper discusses directional stability and course keeping of fast monohulls. Model tests and CFD were used for analysis. In itself these are great tools, but in early design stage they are often perceived as too elaborate. In comparison, design verification is often carried out during model testing., However, it is not common to use these model tests for systematic variation or multiple design variations. In addition to model tests, tools for early design assessment are also pursued. By using a 3D panel method, maneuvering coefficients and subsequently directional stability are found in an earlier stage of the design. The present paper describes which methods can be used in the design stage, and some pros and cons of these methods. A method of choice is selected and an example is elaborated. The example ship is a high speed monohull (Fn=0.8) propelled by waterjets. This paper illustrates that the forces acting on the ship while performing forced motions are predicted. A next step (not in the present paper) is to solve the equations of motions in the time domain as a system of ordinary differential equations. However, in order to correctly predict the motions and trajectories, the correct prediction of forces and moments is essential.